Absorbent structures used in diapers, incontinence products and the like, must have the ability to rapidly take-up and retain body fluids which are released in an appreciable quantity over a relatively short period of time. To achieve this objective, the absorbent structure should be able to rapidly capture the onrush of fluid to prevent the fluid to leak past the edges of the absorbent structure, disperse by wicking action the captured fluid mass within the entire available absorbent volume, and lock the absorbed fluid therein to prevent leak-through and wet-back failures.
An absorbent structure which has been found particularly successful in this regard is a combination of a highly permeable fluid transfer sheet, such as pulp, exhibiting an extremely short fluid penetration time, and a highly absorbent and wicking laminated reservoir, made from peat moss material for example, in intimate fluid communicative relationship with the fluid transfer sheet, whose purpose is to permanently retain the absorbed fluid. This composite absorbent structure combines the desirable advantages of fairly rapid fluid penetration, high absorption and excellent wicking power contributing to reduce failures.
To further enhance the fluid absorption characteristics of the composite absorbent structure, it has been suggested to provide the laminated reservoir with a fluid distribution well in the inner reservoir layer. (For the purpose of this specification, the terms "inner layer" and "outer layer" will be used to designate the various layers of the laminated reservoir by their positions with respect to the fluid transfer sheet. "Inner" denotes a position closer to the fluid transfer sheet, while "outer" refers to a position farther from the fluid transfer sheet). The purpose of the well is twofold. Firstly, it exposes the outer layer to the fluid transfer sheet, through an opening in the inner layer, thereby increasing the surface area of the laminated reservoir capable to take-up fluid. Secondly, the well has the ability to distribute a coherent mass of fluid released from the fluid transfer sheet, along the laminated reservoir from the point of impact to prevent local saturation and overflow leakage.
Although composite absorbent structures of the type described above perform relatively well, it is desirable to further improve their fluid absorption characteristics.